The following relates generally to wireless communication, and more specifically to using subarrays of a beamformer to transmit control channels from a base station in a forward link. Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple mobile devices. These mobile devices may be ground-based or located in an airborne vehicle such as an airplane or helicopter. Base stations may communicate with mobile devices on forward and reverse links. Each base station has a coverage range, which may be referred to as the coverage area of the cell.
Base stations may be equipped with an array of antenna elements which transmit together to form a narrow beam aimed at a single mobile device. In some cases, however, more than one mobile device will inhabit a single cell. When this happens, the base station may wish to communicate common information to every mobile device in its coverage area simultaneously. This may require communicating over a broad angular range (azimuth). To communicate over a broad angle, the base station may transmit using a single antenna element rather than using all of its antenna elements. A single antenna, however, transmits at a high power level in order to reach the edges of the cell, and this presents a constraint on antenna design at the base station.